The present invention is directed to a micro device and to an actuator device for operating a micro device. More particularly, the invention is directed to a valve structure for use in a microfluidic device and to a micro device for actuating a microvalve.
Various micro devices are known in the art for performing different tasks. One application that has received interest in recent years is in the field of fluid control devices and particularly microvalves. The microvalves have been shown to be useful in many industrial applications including the field of drug delivery, fuel delivery systems for internal combustion engines, as well as ink jet printers. These devices have been made by a number of different processes.
The many techniques that are commonly used in the fabrication of electronic devices and integrated circuit chips are suitable for micromachining of micromechanical devices. These micro devices are typically referred to as micro-electrical mechanical systems (MEMS). The devices are extremely small and can be made from numerous kinds of materials. A common material is silicon in the form of silicon wafers used in the integrated circuit industry. Other materials that can be used include glass and ceramics.
An example of a microvalve is disclosed in U.S. Pat. No. 6,056,269 to Johnson et al. The microvalve disclosed therein includes a silicon diaphragm with a valve seat and a flow channel. The diaphragm is positioned so it is able close against the valve seat when the diaphragm is deflected. A separate actuating force is applied to the diaphragm to open and close the valve. The actuating device can be a pressurized fluid or a solenoid mechanism to apply a force to one side of the diaphragm.
Solenoid actuation of a valve in a gas chromatography assembly is known as disclosed in U.S. Pat. No. 4,582,624 to Terry et al. These devices are not always effective in actuating the valve structure since the actuation force can be difficult to control and provide sufficient force. The solenoid actuated devices are also expensive to produce and portions of the device can not be manufactured efficiently.
Another microactuator device is disclosed in U.S. Pat. No. 5,344,117 to Trah et al. The actuator is made from a silicon body having a bending element that is able to bend within a recess formed in the bottom of the silicon body. A force element is coupled to the top surface of the bending element to cause the deflection of the bending element. The force element is disclosed as operating on a thermal expansion and contraction.
Another manner of actuating a microvalve device is by the use of electrostatic force to deflect a flexible diaphragm. The diaphragm is used to seal the outlet of the valve by contacting the valve seat. It has been found that the electrostatic force cannot be produced in a reliable and consistent manner. An example of this type of device is disclosed in U.S. Pat. No. 452,624.
Micro pumps are also known for various uses and particularly for a driving an inkjet printer. These pumps typically have a piezoelectric crystal fitted to a membrane that is able to move the membrane and cause the pumping action. A disadvantage of this type of device is that the device is affected by temperature since the membranes can deform with temperature changes.
Another type of micro device is actuated by an electrically driven actuator. One example is a device that has a plurality of legs made from a bimetallic material. The bimetallic legs are heated to cause stresses and deflection in the legs due to the unequal expansion coefficient. The deflection of the legs actuates the device. This is a typical manner of actuating a microvalve since the actuator is able provide control to increase or decrease the fluid flow through an orifice.
Other microvalve structures and methods of controlling and actuating the valve are disclosed in U.S. Pat. No. 5,058,856 to Gordon et al., U.S. Pat. No. 5,780,780 to Barth, U.S. Pat. No. 5,681,024 to Lisec et al. and U.S. Pat. No. 5,429,713 to Stevenson et al.
The prior devices for controlling micro devices and particularly microvalves have been successful for many purposes but have met with limited success for others. Accordingly there is a need in the industry for an improved actuating devices for various micro devices.
The present invention is directed to a micro device and to an actuator device for operating a micro device. More particularly, the invention is directed to a microfluidic device such as a microvalve and to an actuator for operating a micro device.
Accordingly, a primary object of the invention is to provide a microvalve that can be used for various medical applications such as in the field of drug delivery.
Another object of the invention is to provide a microvalve that can be manufactured by micromachining techniques.
A further object of the invention is to provide a microactuator that can be manufactured by microelectromechanical processes.
Still another object of the invention is to provide a microvalve having a minimal number of moving components and is economical to produce.
Another object of the invention is to provide a microvalve having a membrane made from a polymeric material that is deformed by applying an electric current to the membrane so that the membrane contacts a valve seat and closes the valve.
A further object of the invention is to provide a microvalve having an electrode pad with a permeation membrane where the thickness of the permeation membrane is expandable by applying an electric current to the electrode.
Another object of the invention is to provide a microvalve having an electrode pad with a water permeable membrane attached thereto and spaced from a valve seat where the membrane deforms in a first direction when a positive charge is applied to the electrode pad and deforms in a second direction when a negative charge is applied.
A further object of the invention is to provide an actuator for a micro device where the actuator includes an electrode and a permeation layer that is deformed when an electric current is applied to the electrode.
Still another object of the invention is to provide an actuator of a micro device having an electrode with a permeation membrane thereon where the membrane expands in a direction perpendicular to the electrode when an electric current is applied.
Another object of the invention is to provide an actuator for a micro device where the actuator impinges on a micro device and is actuated by selectively applying either a positive charge or a negative charge to the actuator.
The various objects and advantages of the invention are basically attained by providing an actuator for a micro device comprising an electrode pad having a water permeable membrane on the electrode pad, and an actuator member contacting the water permeable membrane. The water permeable membrane is selected to expand and contact when an electric current is applied to the electrode pad in order to move the actuator member.
The objects of the invention are further attained by providing a microvalve comprising a base substrate having at least one electrode pad with a permeation membrane on the electrode pad. The permeable membrane is deformable when an electric current is applied to the electrode. A top wall is spaced from the water permeable membrane to define a fluid path between the top wall and the water permeable membrane. The permeation membrane is deformable when an electric current is applied to substantially close the fluid path.
The objects of the invention are further attained by providing a method of actuating a valve assembly of a microfluidic device, where the method comprises providing a microfluidic valve assembly having a base substrate with at least one electrode pad, and a deformable water permeable membrane on the electrode pad. A top wall is spaced from the water permeable membrane to form a fluid path between the water permeable membrane and the top wall. An electric current is applied to the electrode pad for sufficient time to expand the water permeable membrane to substantially close the fluid path.
The objects, advantages and other salient features of the invention will become apparent to one skilled in the art in view of the following detailed description of the invention in conjunction with the annexed drawings, which form a part of this original disclosure.